To reduce system in-rush current, conventional power supplies may employ so-called “soft-start” techniques to gradually bring the output voltage up to a nominal level. In some DC-DC converters, a control loop with feedback from the output voltage is used for output voltage regulation in normal operation as well as during startup. Typically, an error comparator is used for such purposes, where the feedback voltage is compared to a reference voltage (and the reference voltage ramps up to some prescribed level). The output of the error comparator may be used, for example, to set the duty cycle of the DC-DC converter switches. However, due to component variation and limitations on the input voltage range of the error comparator, low values of feedback voltage and ramp reference voltage during startup may cause significant input voltage droop, input surge current and output voltage jumps. Such events may trigger system shutdown and/or loss of functionality or performance of various system components. In addition, output voltage jumps may trigger ESD protection circuits, which could result in system malfunction and/or damage.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art.